The present invention relates to a data communication system and method and a server which perform data communication by using the MITF (Mobile Internet Access Forum) dial-up dormant protocol which is a procedure for controlling connection by activating/inactivating data using the Internet.
In ARIB (Association of Radio Industries and Businesses) STD-T78 as a standard specification established by the ARIB, the specification of the MITF dial-up dormant protocol is defined, which is a procedure for controlling connection by using a transmission control function such as PIAFS (PHS Internet Access Forum Standard) and ISDN (Integrated Service digital Network) and activating/inactivating data using the Internet.
FIG. 3 shows a communication environment to which the MITF dial-up dormant protocol written in ARIB STD-T78 is applied. As shown in FIG. 3, in a data link starting side 1 and data link started side 2 connected to each other through a physical line, the dormant procedure of the MITF dial-up dormant protocol is located between a high-level protocol and a transmission control procedure as an upper layer relative to a physical layer. In this case, the physical layer is a layer for converting an output signaling system into a form matching the physical line, and the high-level protocol is a protocol dependent on an application program for facsimile communication, PC communication, Internet communication, or the like.
The MITF dial-up dormant procedure is constituted by a procedure on the data link starting side 1 which generates a dormant request and a procedure on the data link started side 2 which receives the dormant request and returns a response. The MITF dial-up dormant protocol provides the high-level protocol with a temporary disconnection function and reconnection function. More specifically, the MITF dial-up dormant protocol provides the high-level protocol with services of encapsulation of data link disconnection (transition to the dormant state) and data link reconnection (return from the dormant state, which is provided from the data link starting side only). The dormant state is a state wherein the link at the physical layer level between the data link starting side 1 and the data link started side 2 is released.
FIG. 4 shows a data communication system to which the MITF dial-up dormant protocol is applied. This data communication system is a system for accessing the Internet from a user terminal used by a user. As shown in FIG. 4, the system is comprised of a data link starting side apparatus 1 serving as a user terminal, a data link started side apparatus 2, Internet 6, a user connection destination server 4 located on the Internet 6, and a circuit switched network 5.
The data link starting side apparatus 1 is a personal computer (to be referred to as a PC hereinafter) or the like. A dormant function based on the MITF dial-up dormant protocol is installed in the data link starting side apparatus 1. The data link starting side apparatus 1 connects to the circuit switched network 5 to perform line control, and makes a data link connection to the data link started side apparatus 2.
The data link started side apparatus 2 performs line control between itself and the data link starting side apparatus 1 by connecting to the circuit switched network 5, and performs LAN control between itself and the user connection destination server 4 through the Internet 6, thereby relaying packets between the circuit switched network 5 and the Internet 6. The data link started side apparatus 2 has a function of holding the originating telephone number of the data link starting side apparatus 1 as internal information and restoring a connection to the previously used user connection destination server 4 at the time of reconnection from the data link starting side apparatus 1. The user connection destination server 4 is a server for providing users with Web and chat, which are generally used on the Internet 6, by connecting to the Internet 6 so as to perform LAN control and data communication.
FIG. 5 shows the dormant function of the data communication system to which the MITF dial-up dormant protocol is applied. As shown in FIG. 5, when the data link starting side apparatus 1 line-connects to the data link started side apparatus 2 by an originating/terminating function (step S101), the originating telephone number of the data link starting side apparatus 1 is stored as internal information in the data link started side apparatus 2 (step S102), and the data link starting side apparatus 1 and data link started side apparatus 2 are set in a speech communication state.
In this state, the data link starting side apparatus 1 accesses the user connection destination server 4 on the Internet 6 through the data link started side apparatus 2 to receive Web data (steps S103 and S104).
According to the MITF dial-up dormant protocol, if no communication done between the data link starting side apparatus 1 and the user connection destination server 4 for a predetermined period of time (no access is made from the data link started side apparatus 2 for the predetermined period of time), the data link starting side apparatus 1 disconnects the line between itself and the data link started side apparatus 2 (step S105). The data link starting side apparatus 1 and data link started side apparatus 2 then shift to a dormant state, and the link at the physical layer level between them is released.
When data is to be transmitted from the high-level protocol to the data link started side while the data link starting side apparatus 1 is in the “dormant state”, the data link starting side apparatus 1 transmits a “reconnection request” after link establishment (MITF dial-up dormant message) to the data link started side apparatus 2. Upon reception of a reconnection response “MITF dial-up dormant message” from the data link started side apparatus 2 afterward, the data link starting side apparatus 1 shifts the communication state to an “active state”. That is, the data link starting side apparatus 1 can perform “reconnection” to the data link started side apparatus 2.
In contrast to this, assume that data addressed to the data link starting side apparatus 1 is transmitted from the user connection destination server 4 to the data link started side apparatus 2. In the dormant state, however, no link at the physical layer level exists between the data link starting side apparatus 1 and the data link started side apparatus 2, and a data link connection based on the MITF dial-up dormant protocol is limited to a connection from the data link starting side, as described above. For this reason, even if data is transmitted from the Internet 6, the data link started side apparatus 2 cannot reconnect to the data link starting side apparatus 1 to transmit the data.
As described above, conventionally, in data communication based on the MITF dial-up dormant protocol, when the data link starting side and data link started side are set in the dormant state, there is no link at the physical layer level exists between them. Even if, therefore, data addressed to the data link starting side is received from the Internet, the data link started side cannot transmit the data to the data link starting side.